You can negotiate your net salary in graduated tax regimes as well. The math isn’t as clean, but as long as the tax calculation is deterministic, you can negotiate a salary so that you get a nice round number in your bank account every month.

For some reason this isn’t common practice. I’ve always found it weird that salaries are quoted in gross amount.

In some cases the round number may not be the “net” amount because eg maybe you have some rental income, or income from last year, moved to a new state, etc. But in most cases it’ll be pretty close.